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                    快速上手
            
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                    基础类型
            
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                    接口
            
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                    类
            
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                    函数
            
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                    泛型
            
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                    枚举
            
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                    类型推论
            
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                    类型兼容性
            
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                    高级类型
            
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                    实用工具类型
            
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                    Symbols
            
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                    Iterators 和 Generators
            
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                    模块
            
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                    命名空间
            
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                    命名空间和模块
            
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                    模块解析
            
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                    声明合并
            
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                    书写.d.ts文件
            
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                    JSX
            
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                    Decorators
            
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                    混入
            
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                    三斜线指令
            
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                    JavaScript文件里的类型检查
            
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                    如何书写声明文件
            
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                    结构
            
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                    规范
            
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                    举例
            
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                    深入
            
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                    发布
            
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                    使用
            
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                    工程配置
            
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                    tsconfig.json
            
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                    工程引用
            
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                    NPM包的类型
            
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        <li class="chapter " data-level="1.5.4" data-path="../handbook/Compiler Options.html">
            
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                    编译选项
            
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        <li class="chapter " data-level="1.5.5" data-path="../handbook/Configuring Watch.html">
            
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                    配置 Watch
            
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        <li class="chapter " data-level="1.5.6" data-path="../handbook/Compiler Options in MSBuild.html">
            
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                    在MSBuild里使用编译选项
            
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        <li class="chapter " data-level="1.5.7" data-path="../handbook/Integrating with Build Tools.html">
            
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                    与其它构建工具整合
            
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        <li class="chapter " data-level="1.5.8" data-path="../handbook/Nightly Builds.html">
            
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                    使用TypeScript的每日构建版本
            
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                    Wiki
            
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        <li class="chapter " data-level="1.6.1" data-path="../wiki/this-in-TypeScript.html">
            
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                    TypeScript里的this
            
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        <li class="chapter " data-level="1.6.2" data-path="../wiki/coding_guidelines.html">
            
                <a href="../wiki/coding_guidelines.html">
            
                    
                    编码规范
            
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        <li class="chapter " data-level="1.6.3" data-path="../wiki/Common Errors.html">
            
                <a href="../wiki/Common Errors.html">
            
                    
                    常见编译错误
            
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        <li class="chapter " data-level="1.6.4" data-path="../wiki/TypeScript-Editor-Support.html">
            
                <a href="../wiki/TypeScript-Editor-Support.html">
            
                    
                    支持TypeScript的编辑器
            
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        <li class="chapter " data-level="1.6.5" data-path="../wiki/Using-TypeScript-With-ASP.NET-5.html">
            
                <a href="../wiki/Using-TypeScript-With-ASP.NET-5.html">
            
                    
                    结合ASP.NET v5使用TypeScript
            
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        <li class="chapter " data-level="1.6.6" data-path="../wiki/Architectural-Overview.html">
            
                <a href="../wiki/Architectural-Overview.html">
            
                    
                    架构概述
            
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        <li class="chapter " data-level="1.6.7" data-path="../wiki/Roadmap.html">
            
                <a href="../wiki/Roadmap.html">
            
                    
                    发展路线图
            
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            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.7" data-path="../release-notes/">
            
                <a href="../release-notes/">
            
                    
                    新增功能
            
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        <li class="chapter " data-level="1.7.1" data-path="../release-notes/TypeScript 3.1.html">
            
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                    TypeScript 3.1
            
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        <li class="chapter " data-level="1.7.2" data-path="../release-notes/TypeScript 3.0.html">
            
                <a href="../release-notes/TypeScript 3.0.html">
            
                    
                    TypeScript 3.0
            
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        <li class="chapter " data-level="1.7.3" data-path="../release-notes/TypeScript 2.9.html">
            
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                    TypeScript 2.9
            
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        <li class="chapter " data-level="1.7.4" data-path="../release-notes/TypeScript 2.8.html">
            
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                    TypeScript 2.8
            
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        <li class="chapter " data-level="1.7.5" data-path="../release-notes/TypeScript 2.7.html">
            
                <a href="../release-notes/TypeScript 2.7.html">
            
                    
                    TypeScript 2.7
            
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        <li class="chapter " data-level="1.7.6" data-path="../release-notes/TypeScript 2.6.html">
            
                <a href="../release-notes/TypeScript 2.6.html">
            
                    
                    TypeScript 2.6
            
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        <li class="chapter " data-level="1.7.7" data-path="../release-notes/TypeScript 2.5.html">
            
                <a href="../release-notes/TypeScript 2.5.html">
            
                    
                    TypeScript 2.5
            
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        <li class="chapter " data-level="1.7.8" data-path="../release-notes/TypeScript 2.4.html">
            
                <a href="../release-notes/TypeScript 2.4.html">
            
                    
                    TypeScript 2.4
            
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        <li class="chapter " data-level="1.7.9" data-path="../release-notes/TypeScript 2.3.html">
            
                <a href="../release-notes/TypeScript 2.3.html">
            
                    
                    TypeScript 2.3
            
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        <li class="chapter " data-level="1.7.10" data-path="../release-notes/TypeScript 2.2.html">
            
                <a href="../release-notes/TypeScript 2.2.html">
            
                    
                    TypeScript 2.2
            
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        <li class="chapter " data-level="1.7.11" data-path="../release-notes/TypeScript 2.1.html">
            
                <a href="../release-notes/TypeScript 2.1.html">
            
                    
                    TypeScript 2.1
            
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        <li class="chapter " data-level="1.7.12" data-path="../release-notes/TypeScript 2.0.html">
            
                <a href="../release-notes/TypeScript 2.0.html">
            
                    
                    TypeScript 2.0
            
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        <li class="chapter " data-level="1.7.13" data-path="../release-notes/TypeScript 1.8.html">
            
                <a href="../release-notes/TypeScript 1.8.html">
            
                    
                    TypeScript 1.8
            
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        <li class="chapter " data-level="1.7.14" data-path="../release-notes/TypeScript 1.7.html">
            
                <a href="../release-notes/TypeScript 1.7.html">
            
                    
                    TypeScript 1.7
            
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        <li class="chapter " data-level="1.7.15" data-path="../release-notes/TypeScript 1.6.html">
            
                <a href="../release-notes/TypeScript 1.6.html">
            
                    
                    TypeScript 1.6
            
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        <li class="chapter " data-level="1.7.16" data-path="../release-notes/TypeScript 1.5.html">
            
                <a href="../release-notes/TypeScript 1.5.html">
            
                    
                    TypeScript 1.5
            
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        <li class="chapter " data-level="1.7.17" data-path="../release-notes/TypeScript 1.4.html">
            
                <a href="../release-notes/TypeScript 1.4.html">
            
                    
                    TypeScript 1.4
            
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        <li class="chapter " data-level="1.7.18" data-path="../release-notes/TypeScript 1.3.html">
            
                <a href="../release-notes/TypeScript 1.3.html">
            
                    
                    TypeScript 1.3
            
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        <li class="chapter " data-level="1.7.19" data-path="../release-notes/TypeScript 1.1.html">
            
                <a href="../release-notes/TypeScript 1.1.html">
            
                    
                    TypeScript 1.1
            
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            </ul>
            
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        <li class="chapter " data-level="1.8" data-path="breaking-changes.html">
            
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                    Breaking Changes
            
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        <li class="chapter " data-level="1.8.1" data-path="TypeScript 2.4.html">
            
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                    TypeScript 2.4
            
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        <li class="chapter " data-level="1.8.2" data-path="TypeScript 2.3.html">
            
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                    TypeScript 2.3
            
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        <li class="chapter " data-level="1.8.3" data-path="TypeScript 2.2.html">
            
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                    TypeScript 2.2
            
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        <li class="chapter active" data-level="1.8.4" data-path="TypeScript 2.1.html">
            
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                    TypeScript 2.1
            
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        <li class="chapter " data-level="1.8.5" data-path="TypeScript 2.0.html">
            
                <a href="TypeScript 2.0.html">
            
                    
                    TypeScript 2.0
            
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        <li class="chapter " data-level="1.8.6" data-path="TypeScript 1.8.html">
            
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                    TypeScript 1.8
            
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        <li class="chapter " data-level="1.8.7" data-path="TypeScript 1.7.html">
            
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                    TypeScript 1.7
            
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                                <h1 id="typescript-21">TypeScript 2.1</h1>
<p>&#x5B8C;&#x6574;&#x7684;&#x7834;&#x574F;&#x6027;&#x6539;&#x52A8;&#x5217;&#x8868;&#x8BF7;&#x5230;&#x8FD9;&#x91CC;&#x67E5;&#x770B;:<a href="https://github.com/Microsoft/TypeScript/issues?q=is%3Aissue+milestone%3A%22TypeScript+2.1%22+label%3A%22Breaking+Change%22+is%3Aclosed" target="_blank">breaking change issues</a>.</p>
<h2 id="&#x751F;&#x6210;&#x7684;&#x6784;&#x9020;&#x51FD;&#x6570;&#x4EE3;&#x7801;&#x5C06;this&#x7684;&#x503C;&#x66FF;&#x6362;&#x4E3A;super&#x8C03;&#x7528;&#x7684;&#x8FD4;&#x56DE;&#x503C;">&#x751F;&#x6210;&#x7684;&#x6784;&#x9020;&#x51FD;&#x6570;&#x4EE3;&#x7801;&#x5C06;<code>this</code>&#x7684;&#x503C;&#x66FF;&#x6362;&#x4E3A;<code>super(...)</code>&#x8C03;&#x7528;&#x7684;&#x8FD4;&#x56DE;&#x503C;</h2>
<p>&#x5728;ES2015&#x4E2D;&#xFF0C;&#x5982;&#x679C;&#x6784;&#x9020;&#x51FD;&#x6570;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x90A3;&#x4E48;&#x5BF9;&#x4E8E;&#x4EFB;&#x4F55;<code>super(...)</code>&#x7684;&#x8C03;&#x7528;&#x8005;&#x5C06;&#x9690;&#x5F0F;&#x5730;&#x66FF;&#x6362;&#x6389;<code>this</code>&#x7684;&#x503C;&#x3002;
&#x56E0;&#x6B64;&#xFF0C;&#x6709;&#x5FC5;&#x8981;&#x83B7;&#x53D6;&#x4EFB;&#x4F55;&#x53EF;&#x80FD;&#x7684;<code>super(...)</code>&#x7684;&#x8FD4;&#x56DE;&#x503C;&#x5E76;&#x7528;<code>this</code>&#x8FDB;&#x884C;&#x66FF;&#x6362;&#x3002;</p>
<p><strong>&#x793A;&#x4F8B;</strong></p>
<p>&#x5B9A;&#x4E49;&#x4E00;&#x4E2A;&#x7C7B;<code>C</code>&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">class</span> C extends B {
    <span class="hljs-keyword">public</span> a: <span class="hljs-built_in">number</span>;
    <span class="hljs-keyword">constructor</span>() {
        <span class="hljs-keyword">super</span>();
        <span class="hljs-keyword">this</span>.a = <span class="hljs-number">0</span>;
    }
}
</code></pre>
<p>&#x5C06;&#x751F;&#x6210;&#x5982;&#x4E0B;&#x4EE3;&#x7801;&#xFF1A;</p>
<pre><code class="lang-js"><span class="hljs-keyword">var</span> C = (<span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params">_super</span>) </span>{
    __extends(C, _super);
    <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">C</span>(<span class="hljs-params"></span>) </span>{
        <span class="hljs-keyword">var</span> _this = _super.call(<span class="hljs-keyword">this</span>) || <span class="hljs-keyword">this</span>;
        _this.a = <span class="hljs-number">0</span>;
        <span class="hljs-keyword">return</span> _this;
    }
    <span class="hljs-keyword">return</span> C;
}(B));
</code></pre>
<p>&#x6CE8;&#x610F;&#xFF1A;</p>
<ul>
<li><code>_super.call(this)</code>&#x5B58;&#x5165;&#x5C40;&#x90E8;&#x53D8;&#x91CF;<code>_this</code></li>
<li>&#x6784;&#x9020;&#x51FD;&#x6570;&#x4F53;&#x91CC;&#x6240;&#x6709;&#x4F7F;&#x7528;<code>this</code>&#x7684;&#x5730;&#x65B9;&#x90FD;&#x88AB;&#x66FF;&#x6362;&#x4E3A;<code>super</code>&#x8C03;&#x7528;&#x7684;&#x8FD4;&#x56DE;&#x503C;&#xFF08;&#x4F8B;&#x5982;<code>_this</code>&#xFF09;</li>
<li>&#x6BCF;&#x4E2A;&#x6784;&#x9020;&#x51FD;&#x6570;&#x5C06;&#x660E;&#x786E;&#x5730;&#x8FD4;&#x56DE;&#x5B83;&#x7684;<code>this</code>&#xFF0C;&#x4EE5;&#x786E;&#x4FDD;&#x6B63;&#x786E;&#x7684;&#x7EE7;&#x627F;</li>
</ul>
<p>&#x503C;&#x5F97;&#x6CE8;&#x610F;&#x7684;&#x662F;&#x5728;<code>super(...)</code>&#x8C03;&#x7528;&#x524D;&#x5C31;&#x4F7F;&#x7528;<code>this</code>&#x4ECE;<a href="#disallow-this-accessing-before-super-call">TypeScript 1.8</a>&#x5F00;&#x59CB;&#x5C06;&#x4F1A;&#x5F15;&#x53D1;&#x9519;&#x8BEF;&#x3002;</p>
<h2 id="&#x7EE7;&#x627F;&#x5185;&#x7F6E;&#x7C7B;&#x578B;&#x5982;error&#xFF0C;array&#x548C;map&#x5C06;&#x662F;&#x65E0;&#x6548;&#x7684;">&#x7EE7;&#x627F;&#x5185;&#x7F6E;&#x7C7B;&#x578B;&#x5982;<code>Error</code>&#xFF0C;<code>Array</code>&#x548C;<code>Map</code>&#x5C06;&#x662F;&#x65E0;&#x6548;&#x7684;</h2>
<p>&#x505A;&#x4E3A;&#x5C06;<code>this</code>&#x7684;&#x503C;&#x66FF;&#x6362;&#x4E3A;<code>super(...)</code>&#x8C03;&#x7528;&#x8FD4;&#x56DE;&#x503C;&#x7684;&#x4E00;&#x90E8;&#x5206;&#xFF0C;&#x5B50;&#x7C7B;&#x5316;<code>Error</code>&#xFF0C;<code>Array</code>&#x7B49;&#x7684;&#x7ED3;&#x679C;&#x53EF;&#x4EE5;&#x662F;&#x975E;&#x9884;&#x6599;&#x7684;&#x3002;
&#x8FD9;&#x662F;&#x56E0;&#x4E3A;<code>Error</code>&#xFF0C;<code>Array</code>&#x7B49;&#x7684;&#x6784;&#x9020;&#x51FD;&#x6570;&#x4F1A;&#x4F7F;&#x7528;ECMAScript 6&#x7684;<code>new.target</code>&#x6765;&#x8C03;&#x6574;&#x5B83;&#x4EEC;&#x7684;&#x539F;&#x578B;&#x94FE;&#xFF1B;
&#x7136;&#x800C;&#xFF0C;&#x5728;ECMAScript 5&#x4E2D;&#x8C03;&#x7528;&#x6784;&#x9020;&#x51FD;&#x6570;&#x65F6;&#x5374;&#x6CA1;&#x6709;&#x6709;&#x6548;&#x7684;&#x65B9;&#x6CD5;&#x6765;&#x786E;&#x4FDD;<code>new.target</code>&#x7684;&#x503C;&#x3002;
&#x5728;&#x9ED8;&#x8BA4;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x5176;&#x5B83;&#x4F4E;&#x7EA7;&#x522B;&#x7684;&#x7F16;&#x8BD1;&#x5668;&#x4E5F;&#x666E;&#x904D;&#x5B58;&#x5728;&#x8FD9;&#x4E2A;&#x9650;&#x5236;&#x3002;</p>
<p><strong>&#x793A;&#x4F8B;</strong></p>
<p>&#x9488;&#x5BF9;&#x5982;&#x4E0B;&#x7684;&#x5B50;&#x7C7B;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">class</span> FooError extends <span class="hljs-built_in">Error</span> {
    <span class="hljs-keyword">constructor</span>(m: string) {
        <span class="hljs-keyword">super</span>(m);
    }
    sayHello() {
        <span class="hljs-keyword">return</span> <span class="hljs-string">&quot;hello &quot;</span> + <span class="hljs-keyword">this</span>.message;
    }
}
</code></pre>
<p>&#x4F60;&#x4F1A;&#x53D1;&#x73B0;&#xFF1A;</p>
<ul>
<li>&#x7531;&#x8FD9;&#x4E2A;&#x5B50;&#x7C7B;&#x6784;&#x9020;&#x51FA;&#x6765;&#x7684;&#x5BF9;&#x8C61;&#x4E0A;&#x7684;&#x65B9;&#x6CD5;&#x53EF;&#x80FD;&#x4E3A;<code>undefined</code>&#xFF0C;&#x56E0;&#x6B64;&#x8C03;&#x7528;<code>sayHello</code>&#x4F1A;&#x5F15;&#x53D1;&#x9519;&#x8BEF;&#x3002;</li>
<li><code>instanceof</code>&#x5E94;&#x7528;&#x4E8E;&#x5B50;&#x7C7B;&#x4E0E;&#x5176;&#x5B9E;&#x4F8B;&#x4E4B;&#x524D;&#x4F1A;&#x5931;&#x6548;&#xFF0C;&#x56E0;&#x6B64;<code>(new FooError()) instanceof FooError</code>&#x4F1A;&#x8FD4;&#x56DE;<code>false</code>&#x3002;</li>
</ul>
<p><strong>&#x63A8;&#x8350;</strong></p>
<p>&#x505A;&#x4E3A;&#x4E00;&#x4E2A;&#x63A8;&#x8350;&#xFF0C;&#x4F60;&#x53EF;&#x4EE5;&#x5728;&#x4EFB;&#x4F55;<code>super(...)</code>&#x8C03;&#x7528;&#x540E;&#x7ACB;&#x5373;&#x624B;&#x52A8;&#x5730;&#x8C03;&#x6574;&#x539F;&#x578B;&#x3002;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">class</span> FooError extends <span class="hljs-built_in">Error</span> {
    <span class="hljs-keyword">constructor</span>(m: string) {
        <span class="hljs-keyword">super</span>(m);

        <span class="hljs-comment">// Set the prototype explicitly.</span>
        <span class="hljs-built_in">Object</span>.setPrototypeOf(<span class="hljs-keyword">this</span>, FooError.prototype);
    }

    sayHello() {
        <span class="hljs-keyword">return</span> <span class="hljs-string">&quot;hello &quot;</span> + <span class="hljs-keyword">this</span>.message;
    }
}
</code></pre>
<p>&#x4F46;&#x662F;&#xFF0C;&#x4EFB;&#x4F55;<code>FooError</code>&#x7684;&#x5B50;&#x7C7B;&#x4E5F;&#x5FC5;&#x987B;&#x8981;&#x624B;&#x52A8;&#x5730;&#x8BBE;&#x7F6E;&#x539F;&#x578B;&#x3002;
&#x5BF9;&#x4E8E;&#x90A3;&#x4E9B;&#x4E0D;&#x652F;&#x6301;<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf" target="_blank"><code>Object.setPrototypeOf</code></a>&#x7684;&#x8FD0;&#x884C;&#x65F6;&#x73AF;&#x5883;&#xFF0C;&#x4F60;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto" target="_blank"><code>__proto__</code></a>&#x3002;</p>
<p>&#x4E0D;&#x5E78;&#x7684;&#x662F;&#xFF0C;<a href="https://msdn.microsoft.com/en-us/library/s4esdbwz(v=vs.94" target="_blank">&#x8FD9;&#x4E9B;&#x53D8;&#x901A;&#x65B9;&#x6CD5;&#x5728;IE10&#x53CA;&#x5176;&#x4E4B;&#x524D;&#x7684;&#x7248;&#x672C;</a>.aspx)
&#x4F60;&#x53EF;&#x4EE5;&#x624B;&#x52A8;&#x5730;&#x5C06;&#x65B9;&#x6CD5;&#x4ECE;&#x539F;&#x578B;&#x4E0A;&#x62F7;&#x8D1D;&#x5230;&#x5B9E;&#x4F8B;&#x4E0A;&#xFF08;&#x6BD4;&#x5982;&#x4ECE;<code>FooError.prototype</code>&#x5230;<code>this</code>&#xFF09;&#xFF0C;&#x4F46;&#x662F;&#x539F;&#x578B;&#x94FE;&#x5374;&#x662F;&#x65E0;&#x6CD5;&#x4FEE;&#x590D;&#x7684;&#x3002;</p>
<h2 id="const&#x53D8;&#x91CF;&#x548C;readonly&#x5C5E;&#x6027;&#x4F1A;&#x9ED8;&#x8BA4;&#x5730;&#x63A8;&#x65AD;&#x6210;&#x5B57;&#x9762;&#x7C7B;&#x578B;"><code>const</code>&#x53D8;&#x91CF;&#x548C;<code>readonly</code>&#x5C5E;&#x6027;&#x4F1A;&#x9ED8;&#x8BA4;&#x5730;&#x63A8;&#x65AD;&#x6210;&#x5B57;&#x9762;&#x7C7B;&#x578B;</h2>
<p>&#x9ED8;&#x8BA4;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;<code>const</code>&#x58F0;&#x660E;&#x548C;<code>readonly</code>&#x5C5E;&#x6027;&#x4E0D;&#x4F1A;&#x88AB;&#x63A8;&#x65AD;&#x6210;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x6570;&#x5B57;&#xFF0C;&#x5E03;&#x5C14;&#x548C;&#x679A;&#x4E3E;&#x5B57;&#x9762;&#x91CF;&#x7C7B;&#x578B;&#x3002;&#x8FD9;&#x610F;&#x5473;&#x7740;&#x4F60;&#x7684;&#x53D8;&#x91CF;/&#x5C5E;&#x6027;&#x53EF;&#x80FD;&#x5177;&#x6709;&#x6BD4;&#x4E4B;&#x524D;&#x66F4;&#x7EC6;&#x7684;&#x7C7B;&#x578B;&#x3002;&#x8FD9;&#x5C06;&#x4F53;&#x73B0;&#x5728;&#x4F7F;&#x7528;<code>===</code>&#x548C;<code>!==</code>&#x7684;&#x65F6;&#x5019;&#x3002;</p>
<p><strong>&#x793A;&#x4F8B;</strong></p>
<pre><code class="lang-ts"><span class="hljs-keyword">const</span> DEBUG = <span class="hljs-literal">true</span>; <span class="hljs-comment">// &#x73B0;&#x5728;&#x4E3A;`true`&#x7C7B;&#x578B;&#xFF0C;&#x4E4B;&#x524D;&#x4E3A;`boolean`&#x7C7B;&#x578B;</span>

<span class="hljs-keyword">if</span> (DEBUG === <span class="hljs-literal">false</span>) { <span class="hljs-comment">// &#x9519;&#x8BEF;&#xFF1A; &#x64CD;&#x4F5C;&#x7B26;&apos;===&apos;&#x4E0D;&#x80FD;&#x5E94;&#x7528;&#x4E8E;&apos;true&apos;&#x548C;&apos;false&apos;</span>
    ...
}
</code></pre>
<p><strong>&#x63A8;&#x8350;</strong></p>
<p>&#x9488;&#x5BF9;&#x6545;&#x610F;&#x8981;&#x6C42;&#x66F4;&#x52A0;&#x5BBD;&#x6CDB;&#x7C7B;&#x578B;&#x7684;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x5C06;&#x7C7B;&#x578B;&#x8F6C;&#x6362;&#x6210;&#x57FA;&#x7840;&#x7C7B;&#x578B;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">const</span> DEBUG = &lt;<span class="hljs-built_in">boolean</span>&gt;<span class="hljs-literal">true</span>; <span class="hljs-comment">// `boolean`&#x7C7B;&#x578B;</span>
</code></pre>
<h2 id="&#x4E0D;&#x5BF9;&#x51FD;&#x6570;&#x548C;&#x7C7B;&#x8868;&#x8FBE;&#x5F0F;&#x91CC;&#x6355;&#x83B7;&#x7684;&#x53D8;&#x91CF;&#x8FDB;&#x884C;&#x7C7B;&#x578B;&#x7EC6;&#x5316;">&#x4E0D;&#x5BF9;&#x51FD;&#x6570;&#x548C;&#x7C7B;&#x8868;&#x8FBE;&#x5F0F;&#x91CC;&#x6355;&#x83B7;&#x7684;&#x53D8;&#x91CF;&#x8FDB;&#x884C;&#x7C7B;&#x578B;&#x7EC6;&#x5316;</h2>
<p>&#x5F53;&#x6CDB;&#x578B;&#x7C7B;&#x578B;&#x53C2;&#x6570;&#x5177;&#x6709;<code>string</code>&#xFF0C;<code>number</code>&#x6216;<code>boolean</code>&#x7EA6;&#x675F;&#x65F6;&#xFF0C;&#x4F1A;&#x88AB;&#x63A8;&#x65AD;&#x4E3A;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x6570;&#x5B57;&#x548C;&#x5E03;&#x5C14;&#x5B57;&#x9762;&#x91CF;&#x7C7B;&#x578B;&#x3002;&#x6B64;&#x5916;&#xFF0C;&#x5982;&#x679C;&#x5B57;&#x9762;&#x91CF;&#x7C7B;&#x578B;&#x6709;&#x76F8;&#x540C;&#x7684;&#x57FA;&#x7840;&#x7C7B;&#x578B;&#xFF08;&#x5982;<code>string</code>&#xFF09;&#xFF0C;&#x5F53;&#x6CA1;&#x6709;&#x5B57;&#x9762;&#x91CF;&#x7C7B;&#x578B;&#x505A;&#x4E3A;&#x63A8;&#x65AD;&#x7684;&#x6700;&#x4F73;&#x8D85;&#x7C7B;&#x578B;&#x65F6;&#x8FD9;&#x4E2A;&#x89C4;&#x5219;&#x4F1A;&#x5931;&#x6548;&#x3002;</p>
<p><strong>&#x793A;&#x4F8B;</strong></p>
<pre><code class="lang-ts"><span class="hljs-keyword">declare</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">push</span>&lt;<span class="hljs-title">T</span> <span class="hljs-title">extends</span> <span class="hljs-title">string</span>&gt;(<span class="hljs-params">...args: T[]</span>): <span class="hljs-title">T</span></span>;

<span class="hljs-keyword">var</span> x = push(<span class="hljs-string">&quot;A&quot;</span>, <span class="hljs-string">&quot;B&quot;</span>, <span class="hljs-string">&quot;C&quot;</span>); <span class="hljs-comment">// &#x63A8;&#x65AD;&#x6210; &quot;A&quot; | &quot;B&quot; | &quot;C&quot; &#x5728;TS 2.1, &#x5728;TS 2.0&#x91CC;&#x4E3A; string</span>
</code></pre>
<p><strong>&#x63A8;&#x8350;</strong></p>
<p>&#x5728;&#x8C03;&#x7528;&#x5904;&#x660E;&#x786E;&#x6307;&#x5B9A;&#x53C2;&#x6570;&#x7C7B;&#x578B;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">var</span> x = push&lt;<span class="hljs-built_in">string</span>&gt;(<span class="hljs-string">&quot;A&quot;</span>, <span class="hljs-string">&quot;B&quot;</span>, <span class="hljs-string">&quot;C&quot;</span>); <span class="hljs-comment">// x&#x662F;string</span>
</code></pre>
<h2 id="&#x6CA1;&#x6709;&#x6CE8;&#x89E3;&#x7684;callback&#x53C2;&#x6570;&#x5982;&#x679C;&#x6CA1;&#x6709;&#x4E0E;&#x4E4B;&#x5339;&#x914D;&#x7684;&#x91CD;&#x8F7D;&#x53C2;&#x6570;&#x4F1A;&#x89E6;&#x53D1;implicit-any&#x9519;&#x8BEF;">&#x6CA1;&#x6709;&#x6CE8;&#x89E3;&#x7684;callback&#x53C2;&#x6570;&#x5982;&#x679C;&#x6CA1;&#x6709;&#x4E0E;&#x4E4B;&#x5339;&#x914D;&#x7684;&#x91CD;&#x8F7D;&#x53C2;&#x6570;&#x4F1A;&#x89E6;&#x53D1;implicit-any&#x9519;&#x8BEF;</h2>
<p>&#x5728;&#x4E4B;&#x524D;&#x7F16;&#x8BD1;&#x5668;&#x9ED8;&#x9ED8;&#x5730;&#x8D4B;&#x4E88;callback&#xFF08;&#x4E0B;&#x9762;&#x7684;<code>c</code>&#xFF09;&#x7684;&#x53C2;&#x6570;&#x4E00;&#x4E2A;<code>any</code>&#x7C7B;&#x578B;&#x3002;&#x539F;&#x56E0;&#x5173;&#x4E4E;&#x5230;&#x7F16;&#x8BD1;&#x5668;&#x5982;&#x4F55;&#x89E3;&#x6790;&#x91CD;&#x8F7D;&#x7684;&#x51FD;&#x6570;&#x8868;&#x8FBE;&#x5F0F;&#x3002;&#x4ECE;TypeScript 2.1&#x5F00;&#x59CB;&#xFF0C;&#x5728;&#x4F7F;&#x7528;<code>--noImplicitAny</code>&#x65F6;&#xFF0C;&#x8FD9;&#x4F1A;&#x89E6;&#x53D1;&#x4E00;&#x4E2A;&#x9519;&#x8BEF;&#x3002;</p>
<p><strong>&#x793A;&#x4F8B;</strong></p>
<pre><code class="lang-ts">declare function func(callback: () =&gt; void): any;
declare function func(callback: (arg: number) =&gt; void): any;

func(c =&gt; { });
</code></pre>
<p><strong>&#x63A8;&#x8350;</strong></p>
<p>&#x5220;&#x9664;&#x7B2C;&#x4E00;&#x4E2A;&#x91CD;&#x8F7D;&#xFF0C;&#x56E0;&#x4E3A;&#x5B83;&#x5B9E;&#x5728;&#x6CA1;&#x4EC0;&#x4E48;&#x610F;&#x4E49;&#xFF1B;&#x4E0A;&#x9762;&#x7684;&#x51FD;&#x6570;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;1&#x4E2A;&#x6216;0&#x4E2A;&#x5FC5;&#x987B;&#x53C2;&#x6570;&#x8C03;&#x7528;&#xFF0C;&#x56E0;&#x4E3A;&#x51FD;&#x6570;&#x53EF;&#x4EE5;&#x5B89;&#x5168;&#x5730;&#x5FFD;&#x7565;&#x989D;&#x5916;&#x7684;&#x53C2;&#x6570;&#x3002;</p>
<pre><code class="lang-ts">declare function func(callback: (arg: number) =&gt; void): any;

func(c =&gt; { });
func(() =&gt; { });
</code></pre>
<p>&#x6216;&#x8005;&#xFF0C;&#x4F60;&#x53EF;&#x4EE5;&#x7ED9;callback&#x7684;&#x53C2;&#x6570;&#x6307;&#x5B9A;&#x4E00;&#x4E2A;&#x660E;&#x786E;&#x7684;&#x7C7B;&#x578B;&#xFF1A;</p>
<pre><code class="lang-ts">func((c:<span class="hljs-built_in">number</span>) =&gt; { });
</code></pre>
<h2 id="&#x9017;&#x53F7;&#x64CD;&#x4F5C;&#x7B26;&#x4F7F;&#x7528;&#x5728;&#x65E0;&#x526F;&#x4F5C;&#x7528;&#x7684;&#x8868;&#x8FBE;&#x5F0F;&#x91CC;&#x65F6;&#x4F1A;&#x88AB;&#x6807;&#x8BB0;&#x6210;&#x9519;&#x8BEF;">&#x9017;&#x53F7;&#x64CD;&#x4F5C;&#x7B26;&#x4F7F;&#x7528;&#x5728;&#x65E0;&#x526F;&#x4F5C;&#x7528;&#x7684;&#x8868;&#x8FBE;&#x5F0F;&#x91CC;&#x65F6;&#x4F1A;&#x88AB;&#x6807;&#x8BB0;&#x6210;&#x9519;&#x8BEF;</h2>
<p>&#x5927;&#x591A;&#x6570;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x8FD9;&#x79CD;&#x5728;&#x4E4B;&#x524D;&#x662F;&#x6709;&#x6548;&#x7684;&#x9017;&#x53F7;&#x8868;&#x8FBE;&#x5F0F;&#x73B0;&#x5728;&#x662F;&#x9519;&#x8BEF;&#x3002;</p>
<p><strong>&#x793A;&#x4F8B;</strong></p>
<pre><code class="lang-ts"><span class="hljs-keyword">let</span> x = <span class="hljs-built_in">Math</span>.pow((<span class="hljs-number">3</span>, <span class="hljs-number">5</span>)); <span class="hljs-comment">// x = NaN, was meant to be `Math.pow(3, 5)`</span>

<span class="hljs-comment">// This code does not do what it appears to!</span>
<span class="hljs-keyword">let</span> arr = [];
<span class="hljs-keyword">switch</span>(arr.length) {
  <span class="hljs-keyword">case</span> <span class="hljs-number">0</span>, <span class="hljs-number">1</span>:
    <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;zero or one&apos;</span>;
  <span class="hljs-keyword">default</span>:
    <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;more than one&apos;</span>;
}
</code></pre>
<p><strong>&#x63A8;&#x8350;</strong></p>
<p><code>--allowUnreachableCode</code>&#x4F1A;&#x7981;&#x7528;&#x4EA7;&#x751F;&#x8B66;&#x544A;&#x5728;&#x6574;&#x4E2A;&#x7F16;&#x8BD1;&#x8FC7;&#x7A0B;&#x4E2D;&#x3002;&#x6216;&#x8005;&#xFF0C;&#x4F60;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;<code>void</code>&#x64CD;&#x4F5C;&#x7B26;&#x6765;&#x9547;&#x538B;&#x8FD9;&#x4E2A;&#x9017;&#x53F7;&#x8868;&#x8FBE;&#x5F0F;&#x9519;&#x8BEF;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">let</span> a = <span class="hljs-number">0</span>;
<span class="hljs-keyword">let</span> y = (<span class="hljs-built_in">void</span> a, <span class="hljs-number">1</span>); <span class="hljs-comment">// no warning for `a`</span>
</code></pre>
<h2 id="&#x6807;&#x51C6;&#x5E93;&#x91CC;&#x7684;dom-api&#x53D8;&#x52A8;">&#x6807;&#x51C6;&#x5E93;&#x91CC;&#x7684;DOM API&#x53D8;&#x52A8;</h2>
<ul>
<li><p><strong>Node.firstChild</strong>&#xFF0C;<strong>Node.lastChild</strong>&#xFF0C;<strong>Node.nextSibling</strong>&#xFF0C;<strong>Node.previousSibling</strong>&#xFF0C;<strong>Node.parentElement</strong>&#x548C;<strong>Node.parentNode</strong>&#x73B0;&#x5728;&#x662F;<code>Node | null</code>&#x800C;&#x975E;<code>Node</code>&#x3002;</p>
<p>&#x67E5;&#x770B;<a href="https://github.com/Microsoft/TypeScript/issues/11113" target="_blank">#11113</a>&#x4E86;&#x89E3;&#x8BE6;&#x7EC6;&#x4FE1;&#x606F;&#x3002;</p>
<p>&#x63A8;&#x8350;&#x660E;&#x786E;&#x68C0;&#x67E5;<code>null</code>&#x6216;&#x4F7F;&#x7528;<code>!</code>&#x65AD;&#x8A00;&#x64CD;&#x4F5C;&#x7B26;&#xFF08;&#x6BD4;&#x5982;<code>node.lastChild!</code>&#xFF09;&#x3002;</p>
</li>
</ul>

                                
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